# Ray Tracing with Sparse Boxes

We present a new method for ray tracing acceleration by modification of current spatial data structures. We augment a spatial hierarchy such as kd-tree with sparsely distributed bounding boxes that are linked from bottom to top. The augmented data structures can be viewed as a hybrid between kd-trees and uniform grids. The augmentation by boxes is used in new traversal algorithms, which are not restricted to start the hierarchy traversal at the root node. This is in particular efﬁcient for short rays where we signiﬁcantly reduce the number of traversal steps through the hierarchy. Further we make use of ray coherence as well as explicit knowledge of ray distribution and initiate the traversal near the leaf nodes where the intersection is expected.